We don’t care if the general public can easily access garlic tablets. We just want to know whether garlic causes a reduction in cholesterol and triglyceride levels in the blood.

Knowing this would be helpful. If the two groups had very different diets, then the first group might have seen greater reductions in their cholesterol and triglycerides not because of the garlic, but because of something else in their diet. If the two groups' diets were similar, that alternate possibility would be ruled out and the argument would be strengthened.

Irrelevant. Even if the effects of garlic don’t kick in until the four-month point, those effects are still real, and might contribute to a reduction in the risk of heart disease.

Irrelevant. We don't know how much garlic is a \"large amount\", and we're not necessarily talking about all patients. The argument is just saying there is a causal connection between consuming garlic and seeing lower levels of cholesterol and triglycerides.

Irrelevant. Whether or not the advertiser cites this study after it was performed doesn't necessarily tell us anything about the study's accuracy.